﻿#region LicenseHeader

// Copyright 2012 The Trustees of Indiana University.  All rights reserved.
// 
// The Indiana University licenses this file to you under the Apache License, 
// Version 2.0 (the "License"); you may not use this file except in compliance 
// with the License.  You may obtain a copy of the License at 
// 
// http://www.apache.org/licenses/LICENSE-2.0
// 
// Unless required by applicable law or agreed to in writing, software 
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
//  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  
// See the License for the specific language governing permissions and 
// limitations under the License.
// 
// @author Thilina Gunarathne (tgunarat@indiana.edu)

#endregion

#region

using System;
using System.Collections.Generic;
using System.Linq;
using AzureMRCore;
using AzureMRCore.DataTypes;
using AzureMRCore.MapRed;

#endregion

namespace PageRankMR
{
    internal class PageRankMerge : Merger<IntKey, DoubleValue, IntKey, DoubleVectorValue, IntKey, DoubleVectorValue>
    {
        public override int Merge(IDictionary<IntKey, List<DoubleValue>> values, string programArgs,
                                  List<KeyValuePair<IntKey, DoubleVectorValue>> dynamicData,
                                  IOutputCollector<IntKey, DoubleVectorValue> outputCollector,
                                  ReduceContext reduceContext, out bool addIteration)
        {
            int numPages = Int32.Parse(programArgs);
            double[] newPageRank = new double[numPages];
            double tanglingPageRank = (values[IntKey.GetInstance(numPages)].FirstOrDefault().Value)/numPages;

            foreach (KeyValuePair<IntKey, List<DoubleValue>> pageInfo in values)
            {
                newPageRank[pageInfo.Key.Key] = ((pageInfo.Value[0].Value + tanglingPageRank)*
                                                 PageRankMR.DANGLING_PROBABILITY) +
                                                ((1 - PageRankMR.DANGLING_PROBABILITY)/numPages);
            }
            outputCollector.Collect(IntKey.GetInstance(0), DoubleVectorValue.GetInstance(newPageRank));
            addIteration = Int32.Parse(reduceContext.ReduceTask.PartitionKey) < 9;
            return 0;
        }
    }
}